1. Field of the Invention
The present invention relates to an information delivery system involving information delivery apparatuses that successively transfer and store information such as subscription news, and an information delivery method employed by the system.
2. Description of the Related Art
An information delivery system such as Internet involves many information delivery apparatuses that are connected to one another through a network. The system delivers information such as subscription news to the apparatuses through the network such that an upstream apparatus transfers the information to a downstream one until every apparatus receives and stores the information.
FIG. 1 is a block diagram showing a conventional information network system. This system involves three information delivery apparatuses 30, 31, and 32 through which information is successively transferred. In particular, the figure shows the details of the intermediate apparatus 31, which is downstream to the apparatus 30 and upstream to the apparatus 32. The apparatuses 30, 31, and 32 have the same configuration.
The apparatus 31 has a delivery controller 1' for receiving information from the upstream apparatus 30 and sending the information to the downstream apparatus 32, a storage unit 3 for storing the information, a storage capacity checker 2 for determining if the storage unit 3 has free space of a predetermined volume, a table 6 for recording the identification data (ID) of information stored in the storage unit 3, a temporary storage unit 9 for temporarily storing information sent from the upstream apparatus 30, and a temporary storage unit 10 for temporarily storing information to be sent to the downstream apparatus 32.
The operation of the system will be explained. In the apparatus 31, the storage capacity checker 2 checks to see if there is free space in the storage unit 3 and passes the result of the check to the upstream apparatus 30. If the free space in the storage unit 3 of the apparatus 31 is below a predetermined volume, the upstream apparatus 30 sends no information to the apparatus 31 and waits until the storage unit 3 of the apparatus 31 has the predetermined free space. The apparatus 31 updates the contents of the storage unit 3 and if the predetermined free space is available in the storage unit 3, the upstream apparatus 30 sends the information to the apparatus 31.
In this system, a network link between the apparatuses 30 and 31 is not used until the storage unit 3 of the apparatus 31 has the predetermined free space. This deteriorates the efficiency of use of the network.
Even if the storage unit 3 of the downstream apparatus 32 has a free space to receive the information, the information will not be transferred to the apparatus 32 because the apparatus 31, which is upstream the apparatus 32, has no space to receive the information. The presence of the apparatus 31 having the insufficient free space causes a delay in transferring the information to the downstream apparatus 32.